We sifted through tons of research on sleep, metabolism, stress, and chronobiology to identify the times when you're most vulnerable to fatigue—and, with expert help, devised a foolproof plan to help you combat it. These eight strategies ensure you will wake up refreshed and recharged, remain alert throughout the day, and wind down just in time for a good night's sleep.

1. When to wake up
Instead of: Sleeping in

Try: Getting up at the same time and bathing yourself in light

This enables your circadian rhythms, which are governed by your body's "master clock" in the hypothalamus gland, to stay in synch with the 24-hour day. In the absence of light, your body's sleep-wake cycle wants to delay by an average of 12 minutes every day and work on a 24.2-hour rhythm. (Scientists don't understand why but think it may relate to the sun's seasonal shifts.) "That means your body wants to keep pushing your bedtime to later," says Mariana Figueiro, PhD, program director of Rensselaer Polytechnic Institute's Lighting Research Center. "But if you let that happen and still have to get up at the same time every day, you're going to be tired."

To keep your circadian rhythms in time with the 24-hour day (when they get out of whack, you feel like you're jet-lagged), aim for 30 minutes of light first thing, even on a Saturday when you've decided to sleep in. An easy way to get it is to go for a half-hour stroll outdoors or have your breakfast by a sunny window. If your schedule requires you to rise when it's dark outside, crank up the lights indoors—every little bit may help.

2. What to eat
Instead of: Loading up on carbs

Try: Limiting them to make room for more protein

Although they can provide a burst of "quick burn" fuel, carbohydrates are an energy drain if you consume too many. Women who reduced the amount of carbohydrates in their diets and raised the amount of protein reported feeling more energetic in recent research done by Donald K. Layman, PhD, a professor of nutrition at the University of Illinois.

Keep your daily intake of healthy carbs below 150 g, best apportioned like this: five servings of vegetables; two servings of fruit; and three or four servings of starchy (preferably whole grain) carbohydrates such as bread, rice, pasta, and cereal. For instance:

Breakfast: one slice of bread or half of an English muffin, one egg, a slice each of ham and cheese, and a glass of milk
Lunch: open-faced sandwich of one slice of bread, 2 to 3 ounces of meat, and 1 ounce of cheese; two servings of vegetables; and an apple
Dinner: 6 ounces of lean meat, three servings of vegetables, one serving of fruit, and one or two servings of starchy carbs

3. When to drink coffee
Instead of: Downing your joe first thing

Try: Having a latte later in the day

That's when you'll really need it. Caffeine keeps you operating at a high level by blocking the effects of adenosine, a sleep-inducing brain chemical that accumulates as the day wears on. By the time adenosine builds up to the point where you start feeling sleepy—generally, late in the afternoon—the effects of your morning caffeine will have worn off, says James K. Wyatt, PhD, director of the Sleep Disorders Service and Research Center at Rush University Medical Center. "Having 1/2 to 1 cup of coffee or its caffeine equivalent during the late afternoon, when the pressure to sleep is high, will keep you energized," he says. But if you're highly sensitive to caffeine's effects, push your break back to early afternoon so you don't have difficulty falling asleep at night. (Did you overdo it? Check out 5 Signs You've Had Too Much Caffeine.)

4. Time your meals
Instead of: Grazing all day long

Try: Eating your meals at the same time every day

Your body's caloric needs are closely tied to its other daily rhythms, including when you get up and go to bed and when you expend the most energy (during your late-day fitness walk, for example). "What will make you tired is if your body expects a 7 a.m. breakfast and a 12 p.m. lunch and you skip one of those," says Layman. "Chaotic eating leads to greater hunger and overeating."

Prepare breakfast the night before so you're sure to start the day with a boost even if you're running late. Pack a lunch to take to work in case you can't get away from your desk midday. On the weekend, make and freeze several meals that you can quickly heat up so you and your family eat dinner at the same time every night. (Need recipes? Here are 16 freezer-friendly ideas.)

5. Relieve stress
Instead of: Meditating for 20 minutes

Try: Shorter, more frequent sessions

"Even in the span of 3 minutes, meditation can decrease the stress hormones that tense your muscles and constrict your blood vessels," says Judith Orloff, MD, a psychiatrist at UCLA and author of Positive Energy. "It increases endorphins too." Quick time-outs throughout your workday are also easier to fit into a busy schedule than a longer one at day's end.

Find a quiet place where you won't be interrupted. ("In a busy office, that may even mean going into the bathroom," says Orloff.) Sit down and close your eyes. Listen to your breath as you slowly inhale and exhale, and when thoughts intrude, imagine that they're like clouds floating by in the sky. Then visualize something or someone who makes you happy. It could be someplace you've been on vacation, someone you love, or something you love doing (like lounging in a fragrant bath).

6. Beat an afternoon slump
Instead of: A power nap

Try: A walk outdoors

Just as it does in the early morning, light later in the day may blunt an afternoon energy dip, which often comes on like clockwork. "Because of the way the homeostatic and circadian systems interact, most people feel a lull 17 to 18 hours after they went to bed the previous night," says Figueiro. Step outside into revitalizing sunlight for a short walk. Vary your routine by taking a different path every day, doing a short errand, or catching up with a friend on your cell phone. If you can't get outside, plant yourself next to a window, open the shades wide, and look out. (For four more ways to get through the day, see How To Prevent An Afternoon Slump.)

7. Get pumped pre workout
Instead of: A light snack

Try: Music

Exercise is a prime energy booster, but what if you're too tired for an antifatigue workout? Put in your earphones while you lace up your walking shoes: Music will help you forget you're whipped. Volunteers who worked out for 30 minutes while listening to tunes felt they weren't exerting themselves as much as when they exercised without music, Japanese researchers reported in the Journal of Sports Medicine and Physical Fitness.

Load your iPod with your favorite up-tempo tunes. If you're the literary type, an audiobook can also help distract you from feelings of fatigue. (What do fitness experts listen to? See Pick A Pro Playlist to steal their tune ideas.)

"Studies show that very bright light—the equivalent to outdoor early morning light—will increase brain activity," says Figueiro. "Our work has shown that you can increase alertness with far less." Some scientists believe that the light emitted by a computer monitor late at night can do just that, confusing your body's sleep-wake cycle.

Wind down by watching television instead. Most people sit far enough away (at least 15 feet) from a TV set to be unaffected by its brightness. Better yet, read a book or magazine. Just make sure the light you use doesn't exceed 60 watts. And log off your computer at least an hour before bed.